“违反诺言”常见的英文表达是 “break one's promise” 。例如：
He broke his promise and never came back.（他违反了诺言，再也没有回来。）
此外，还可以用 “go back on one's word” 来表达相同意思，例如：
She went back on her word and didn't help me as she had said she would.（她违反了诺言，没有像她说的那样帮助我。）